DISEASES OF AQUATIC ORGANISMS Vol. 25: 33-37.1996 1 Published May 9 Dis Aquat Org

Diseases of salmonids resembling myxosporean whirling disease, and the absence of Myxosoma cerebralis, in South America

'Department of and Oceans, Pacific Biological Station. Nanaimo, British Columbia, Canada V9R 5K6 'Servicio de Ictiopatologia, Areas de Acuicultura y Medio Ambiente, Departamento de Recursos Marinos, Fundacion, Castro. Chile

ABSTRACT: Previously publ~shed reports of whirling disease (WD) of salmonids (rainbow rnykiss, chinook 0. tshawytscha and 0. kisutch) in 4 South Arneri- can countries (Venezuela, , , Chile) are reviewed. The disease(s) were shown not to be associated with infections with the myxosporean cerebralis, the cause of myxosporean WD. Our recent observations in Ecuador and Chile of salmonid diseases with clinical signs resembling those of myxosporean WD further demonstrated that the diseases in South America were not caused by M. cerebralis. In Chile, the diseases in coho salmon and were attributed to bacterial infections, whereas no infectious agent was associated with afflicted rainbow trout in Ecuador We con- clude that myxosporean WD of salmonids does not occur in South America. The causes of several other diseases of salmonids with clinical signs similar to those of myxosporean WD (e g whirling behaviour. skeletal deformities, blackened tails) include bacter~alor microsporidial infections of the meninges or brain, myxobacterial infections of the vertebrae, and dietary deficiencies. A diagnosis of myxosporean MID, therefore, cannot be made on clinical signs alone. Laboratory confirmation of the diagnosis through demonstration of the presence of M. cerebralis is necessary.

KEYWORDS: Whirling disease . A4yxobolus cerebralis. Salmonids . Skeletal deformities . Spiral swim ming . Flexibacterpsychrophilus . Renibacterium salmoninarum . South America

INTRODUCTION In South America, diseases with clinical signs resem- bling those of typical myxosporean WD have been Whirling disease (WD) is an ailment of rainbow trout reported since the early 1970s in several populations of Oncorhynchus rnykissfirst described in Germany by rainbow trout and other salmonids. Although these dis- Hofer (1903). The disease is caused by the myxo- eases have been identified as 'whirling disease,' labo- sporean Myxobolus cerebralis Hofer, 1903, which in- ratory confirmation of the diagnosis through demon- fects cranial and other cartilaginous skeletal elements. stration of the causative agent A4yxobolus cerebralis It is now known from most countries in continental has not been accomplished. Nevertheless, in some Europe and from the former USSR, and has been intro- recent reviews (e.g. Schaperclaus 1986, Hoffman 1990) duced to the United States, New Zealand, South certain South American countries still have been Africa, and the British Isles (Hoffman 1970, 1990, included in the geographic range of myxosporean WD. Markiw 1992). Herein we refer to this disease as myxo- It is important to clarify the status of WD in South sporean WD. Signs of the disease include whirling in a America because of potential implications for interna- horizontal plane (known as 'tail-chasing'), deformities tional fish health protection measures that might be of the head, spinal curvature, shortened opercula, and applied to trade in live salmonids and food products blackening of the caudal region (Hoffman et al. 1969, derived therefrom. Cordero del Campillo et al. 1975, Halliday 1976, In the present paper we review the validity of the Schaperclaus 1986, Markiw 1992). reported occurrences of WD in South America, and

O Inter-Research 1996 Resale of full article not permitted Dis Aquat Org 25: 33-37. 1996

report on new studies in Chile and Ecuador on dis- including 2 that were mentioned in Anonymous eases of salmonids with clinical signs resembling those (1972). The failure to detect Myxobolus cerebralis in of myxosporean WD. any of these fish led Conroy (1975, 19811 to conclude that rnyxosporean WD does not exist in Colombia. One of the signs of the disease investigated by Con- HISTORICAL REVIEW roy (1975) was whirling around the longitudinal axis of the fish, in contrast to the horizontally circular The first report of WD in South America was based on whirling in the form of tail-chasing that is characteris- a misinterpretation by Bogdanova (1968, 1970) of a pa- tic of WD caused by M. cerebralis. Apparently, the per published in Venezuela by Martinez (1966). Several report of WD in Anonymous (1972) involved an incor- other authors followed Bogdanova in listing Venezuela rect diagnosis based solely on clinical signs without as a country from which WD has been reported (Anony- laboratory confirmation. mous 1969, Hoffman et al. 1969, Christensen 1973, At about the same time that the reports from Vene- Cordero del Campillo et al. 1975). Although Martinez zuela and Colombia appeared in the literature, a brief (1966) discussed WD (= 'Lentosporidiasis') as a serious note in the FAO Bulletin, attributed to problem in trout rearing, he did r~oistdie 01 i~lipiyihdi it ivieschkat (197i), reported the occurrence oi WD in 2 occurred in Venezuela. Hoffman & Meyers (1969) trout hatcheries in Ecuador. All infected fish had been dropped Venezuela from the list of WD-affected coun- raised from eggs imported from Colombia. The note tries stating that the authorities concerned deny the stated that the 2 hatcheries were infected with presence of WD there. Presumably on the strength of Myxobolus cerebralis. However, Dr Meschkat (pers. this information, Hoffman (1970) and Bogdanova (1973) comm. to the first author, October 3, 1975) advised that deleted Venezuela from the countries in which WD has his diagnosis was based on external signs only and that appeared, although Schaperclaus (1986) continued to affected fry were not examined microscopically. Con- include it. roy (1981) reported a similar response to his enquiries According to Marin-Aponte et al. (1974), Espinoza & about the disease in Ecuador. It seems likely that the Diaz-Ungria (1970) observed rainbow trout in Vene- disease reported from Ecuador is the same as that zuela with signs of WD and assumed, without labora- investigated by Conroy (1975) in Colombia and is not tory confirmation, that the disease was caused by myxosporean WD. Myxobolus cerebralis. Diaz-Ungria (1970) also re- The inclusion of Colombia and/or Ecuador by Cord- ferred to the occurrence of WD in trout, as well as in ero del Campillo et al. (1975), Christensen (1973), and Mugil brasiliensis and Cynoscion sp., in Venezuela. Halliday (1976) among the countries that have experi- Prof. Diaz-Ungna subsequently advised the first author enced myxosporean WD apparently stems from the (pers. comm., July 13, 1976) that M. cerebralis was not original FAO reports. Despite Conroy's (1975, 1981) isolated from these fish and that it was necessary to results and views about the nature of the disease conclude that myxosporean WD has not been demon- reported from Colon~biaand Ecuador, Hoffman (1990) strated to exist in Venezuela. continued to list these countries among those with a Martinez (pers. comm. to the first author, April 20, history of myxosporean WD. 1970), Marin-Aponte et al. (1974), Marin (1974-75), Apparently, the least known report (Anonymous Halliday (1976), Ghittino & Vigliani (1978),and Conroy 1974) of WD in a South American country is that for (1981) all have stated that WD is absent from Vene- Chile. This anonymously authored report, prepared by zuela. Marin-Aponte et al. (1974) investigated a ram- the Division de Pesca y Caza, Servicio Agricola y bow trout disease in Venezuela having signs resem- Ganadero, Ministeria de Agricultura, on aquaculture bling myxosporean WD, but histological examination in Chile, noted that 'mixosomiasis' (= WD) has been revealed that Myxobolus cerebralis was not the diagnosed there in Pacific salmon. No further details causative agent. Possibly, the disease they studied and were provided. According to a former Director of the that observed by Espinoza & Diaz-Ungria (1970) and Division Protection Pesquera, Chile (pers. comm. to Diaz-Ungria (1970) were the same as that reported the first author, October 15, 1976), the affected species later from Colombia by Conroy (1975). were Oncorhynchus kisutch (coho salmon) and 0. Conroy's (1975) interest and study of the disease in tshawytscha (), and the diagnosis was Colombia followed from an anonymously authored based on clinical signs without laboratory confirmation item in the FAO Fish Culture Bulletin (Anonymous of the presence of Myxobolus cerebralis. Under these 1972) reporting that WD occurred in rainbow trout circumstances, the diagnosis must be considered sus- from 4 Colombian trout rearing facilities. Conroy pect and requiring confirmat~on. (1975) undertook deta~ledstudies of afflicted rainbow To complete the historical review, we note that Mar- trout in several hatcheries and fish farms in Colombia, ques-Mendes (1980) reported Myxosorna (= Myxobo- Margolis et al.: Diseases resembl~ngmyxosporean whirling disease

lus) cerebralis as the cause of scoliosis in Muyil Chile brasiliensis from the southern coast of Brazil. No evi- dence was presented to support this diagnosis. As part of routine diagnostic work conducted over the last 5 yr at several private salmonid hatcheries and lake and seawater netpen farms, several cases of dis- RECENT OBSERVATIONS eases with clinical signs of WD have been observed by one of the authors (P.B.)(Table 1).Following extensive Ecuador laboratory examinations, including examinations of heads by the plankton centrifuge method (O'Grodnick In March 1994, one of us (M.K.)had the opportunity 1975). Myxobolus cerebraliswas not detected in any of to examine rainbow trout with clinical signs of WD at a these cases. In addition, M. cerebralis was not found in hatchery in the Riobamba region, Ecuador. One stock numerous clinically normal coho salmon and Atlantic of yearling rainbow trout exhibited a variety of clinical salmon salar that were examined by the plank- changes suggestive of myxosporean WD, including ton centrifuge method to meet U.S. Title 50 import reg- whirling swimming, black tails, deformed vertebral ulations. columns, and flattened noses. Some fish also exhibited darkening on one half of the body exactly along the medial line. Other fish exhibited chaotic swimming DISCUSSION behaviour with no obvious skeletal deformities. Approximately 30% of the fish (about 200) exhibited Although there have been several occurrences of one or more of these changes. diseases in cultured salmonids with clinical signs The heads, pieces of vertebral column, and visceral resembling myxosporean WD in South America, the organs from 5 fish with skeletal deformities were pre- historical evidence and our recent observations failed served in Davidson's solution and processed for histo- to associate Myxobolus cerebralis with these diseases. pathology. Affected skeletal areas exhibited deforma- Several other diseases may cause whirling behaviour tion of the , massive periosteal proliferation, and or skeletal deformities in salmonid fishes. Brocklebank fibroplasia. Thorough microscopic examination of et al. (1995) observed spiral swimming behaviour of bone and sections revealed no myxosporean reared in seawater netpens associated trophozoites or spores. with a microsporidium in the hindbrain. A recently

Table 1.Recent diseases of salmonid fishes in Chile with various clinical signs of whirling disease

Species Developmental Habitat Clinical signs Etiology Date References stage

Coho salmon, Alevins Freshwater, Spiral swimming, tail chasing Unknown Apr-Jul Authors' rainbow trout raceways 1994 unpubl. data

Rainbow trout Fry, alevins Freshwatr~, Swlmming in splral and on Flexibacter Oct 1994 Bustos et al. lake pens sides psychrophilus (1995) and hatcheries

Coho salmon Juvenile Freshwater, Spiral swimming on longitudi- Flexibacter Late 1994, Entrala et al. lake pens nal axis and horizontally, leth- psychrophilus early l995 (1996) argy, exophthalmia, scoliosis, retrocranial swelling, darkening of body on medial hne, black tail, peduncle malfunctions

Rainbow trout Juvenile Freshwater, Tail-chasing, circular Unknown Late 1994. Authors' lake pens swimming on sides early 1995 unpubl. data

Atlantic and Juveniles and Freshwater Swlmming on sides and Renfbacterium Various Bustos et al. coho salmon adults (from and seawater whirling salmoninarum cases, (1992) post-smolt to netpens 1991-1995 harvest size) 36 Dls Aquat Org

described retrovirus-like virus that infects the brain ology of fishes. The University of Wisconsin Press, Madi- causes abnormal spinning motion in various salmonid son. p 769-789 Bogdanova EA (1968) Modern data on the distribution and species in Japan (Oh et al. 1995). Bacterial infections of biology of &Iyxosonla cerebrdlis (, Cnidosporidia) the meninges or brain by Flexibacter psychrophilus (= as agent of whirling disease of salmonids. Bull Off Int Epiz Cytophaga psychrophila) In coho salmon (Kent et al. 69:1499-1506 1989, Entrala et al. 1996) or rainbow trout (Bustos et al. Bogdanova EA (1970) On the natural nidus of whirling dis- 19951, and Renibacterium salmoninarum in Atlantic ease of salmonids and the methods of its formation. Vopr Prirod Ochagovost Bolez 3.147-154 (in Russian) and coho salmon (Bustos et al. 1992, Speare et al. Bogdanova EA (1973) A summary of worldwide investigations 1993), also cause spiral swimming behaviour. Further- on whirling disease of salmonids. In: Dill WA (ed) Sympo- more, chronic infections of vertebrae by F psy- sium on the major communicable fish diseases in Europe chrophilus also cause spinal deformities that may be and their control. Panel reviews and relevant papers. suggestive of myxosporean WD (Conrad & DeCew EIFAC Tech Pap l? (Suppl2):231-239 Brocklebank JR, Speare DJ, Kent ML (1995) Microsporidian 1967). encephalitis of farmed Atlantic salmon (Salmo salar). Can Ascorbic acid deficiencies may also cause skeletal Vet J 36:631-633 anomalies in fish (Ashley et al. 1975). Black tails, lor- Bustos P, Calbuyahue J, J, Opazo B, Entrala P, Sol- dosis, scc!icsis, acc! f!attcnrd heads [all :ypica! signs of ervicens R (1995) Firs! iso!atinr. nf F!o.u!'hac!~rpsyckrc philus, as causative agent of rainbow trout fry syndrome myxosporean WD) were observed in salmonids reared (RTFS), producing rainbow trout mortality in Chile. Bull in Portugal, and extensive examination of these fish Eur Ass Fish Pathol 15:162-164 did not reveal Myxobolus cerebralis infections (Wolf et Bustos P, Poblete A, Navarro J, Montana J (1992) Reportes de al. 1981). No infectious agents were associated with meningo-encefalitis asociado a transtornos conductuales this condition and the authors attributed the disease to por BKD (bacterial kidney disease) en salmon coho (0. kisutch) en la X y XI1 region, Chile. XI11 Panamerican or ascorbic acid deficiencies. Congress of Vetennary Medicine, Santiago, p 366 In Chile the recent cases of diseases resembling WD Christensen NO (1973) Whirling disease (Myxosomiasis) in were attributed to bacterial infections (Table l), but it salmonids. In: DIU WA (ed) Symposium on the major com- is unknown if any of these were the cause of a similar municable fish dlseases in Europe and their control. Panel reviews and relevant papers. EIFAC Tech Pap 17 (Suppl disease in Chile briefly reported in 1974 (Anonymous 2):218-223 (French version, p 224-230); references, 1974). The results of our recent observations on rain- p 237-239 bow trout from Ecuador are similar to those previously Conrad JF, DeCew M (1967) Observations on deformed juve- reported from the study of afflicted trout in Colombia nile coho salmon. Fish Comm Oregon Res Briefs 13:129 and Venezuela in that skeletal abnormalities were Conroy DA (1975) Informe sobre las enfermedades de la trucha arco iris (Salmo gairdnerii) en Colombia. Proyecto prominent and the lesions were not associated with an para el desarrollo de la pesca continental, INDERENA- infectious agent. FAO, Pub1 no. 1, Bogota, p 1-37 In conclusion, as pointed out by Wolf et al. (1981), Conroy DA (1981) The importance of fish diseases in relation confirmation of myxosporean WD must include micro- to the development of salmonid culture in South America. Rev ltal Piscicolt Ittiopatol 16:57-64 scopic detection of Myxobolus cerebralis, and based on Cordero del Campillo M, Escudero-Diez A, Alvarez-Pellitero the evidence to date, M, cerebralis and myxosporean MP, Rojo-Vazquez FA (1975) Torneo de la trucha (myxo- WDdo not occur in South America. To avoid further somosis). Revision Suppl Cient Bol Inform Cons Gen confusion, diseases showing spiral or whirling behav- Coleg Vet Esparia 201 5-28 iour or skeletal deformities in the absence of M, cere- Diaz-Ungria C (1970) Parasitologia de 10s animales domesti- cos en Venezuela, Vol I Univers~dad del Zulia Consejo bralis should not be called 'whirling disease' or the de Desarrollo Cientifico y Humanist~co, Maracaibo, Spanish equivalent 'enfermedad de torneo'. p 779-783 Entrala P, Bustos P, Montana J, Opazo B,Calbuyahue J (1996) First isolation of Cytophaga psychrophila [F, psychro- philus) as a causative agent of nervous disorder in finger- LITERATURE CITED ling coho salmon (Oncorhynchus kisutch) in Chile. Bull Eur Ass Fish Pathol (in press) Anonymous (1969) Whirling disease. FAO Fish Cult Bull Espinoza V, Diaz-Ungria C (1970) Presencia de la enfermedad 1(2):10 del 'torneo' en peces de Venezuela. Proyecto MAC-FAO, Anonymous (1972) Whirling disease in Colombia. FAO Aqua- Facultad de Ciencias Veterinarias de la Universidad del cult Bull 4(3):11-12 Zulla, Maracaibo Anonymous (1974) Situacion actual de la acuicultura conti- Ghittino P, Vigliani E (1978) La mixosomiasi della trota: una nental en Chile. Simposio FAO/CARPAS Sobre Acui- vecchia parassitosi d'importanza attuale. Riv Ital Piscicolt cultura en America Latina, Montevideo, Uruguay, 26 de Ittiopatol 13:15-20, 49-58 noviembre a1 2 de diclembre de 1974. CARPAS/6/74/SC8. Halliday MM (1976) The biology of ~Myxosomacerebralis: the Oct 1974 FAO, R0m.e causative organism of whirling disease of salmonids. Ashley LM, Halver JE, Smith RR (19751 Ascorbic acid defi- J Fish Biol 9(4):339-357 clency In rainbow trout and coho salmon and effects on Hofer B (1903) Uebcr die Drehkrankhelt der Regenbogen- wound healing. In: Ribelin WE, Migaki G (eds) The path- forelle. Allg FischZtg 28:7-8 Margolls et a1 Diseases resembling myxosporean whlrling disease

Hoffman GL (1970) Intercontlnental and transcont~nentaldls- 11, Oct 1974 FAO, Rome semination and transfaunatlon of fish parasites with Markiw ME (1992) Salmonld whlrl~ngdisease. US Dept Int, emphasis on whirling d~sease(Myuosoma cerebralls) In Fish Wildl Serv, Fish Wildl Leaf1 17 Snleszko SF (ed) A symposium on dlseases of flshes and Marques-Mendes A (1980) Patologia de peixes Cienc Cult shellfishes Am Fish Soc Spec Pub1 5 69-81 32 1532-1533 Hoffman GL (1990) M~ixoboluscerebrahs a worldw~decause of Martinez CK (1966) Contribuclon a1 estudlo de las enfer- salmonld whirllng dlsease J Aquat Anim Health 2 30-37 medades de las truchas en Venezuela Bull Off Int Epiz 65. Hoffman GL Dunbar ( C Bradford A (1969) Whirllng disease 1135-1162 of caused by Myxosorna cereblalis In the LTn~ted Meschkat A (1971) Whirling d~sease in Fcuador. FAO States US Fish & LVlldl Selvlce Spec SCI Rep, Flshenes Aquacult Bull 3121.1 1 No 427 (with addendum), Washington, DC O'Grodnlck JJ (1975) Whirllng dlsease iMyxosoma cerebralls Hoffman GL Meyers U (1969) Occurrence of wh~rlingdis- spore concentratlon uslng the continuous plankton cen- ease FAO Flsh Cult Bull 2(1) 13 tnfuge J Wildl Dls 11:54-57 Kent ML, Groff Jbl, Mornson JK Yasutake WT, Holt RA Oh MJ, Yoshimlzu M, Kimura T, Ezura Y (1995) A new virus (1989) Splral swlmmlng behavlour due to cranlal and ver- isolated from salmonid flsh. Fish Path01 30:23-32 tebral leslons assoc~ated wlth ( ytophaga psychrophlla Schaperclaus W (1986) Fish dlseases, Vol 2 Akademie-Ver- infections In salmonld flshes Dls Aquat Org 6 11-16 lag, Berlin, p 597-1398 (English translation, 1991, US Dept Marin C (1974-75) Whirling disease absent In Venezuela Commerce, National Technical Information Service, FAO Aquacult Bull 7(1-2) 21-22 Springfield, VA) Marin-Aponte C, de Urbina FR Lozano 0, de Peraza LA Speare DJ, Ostland VE, Ferguson HW (1993) Pathology asso- (1974) Investigaciones sobre un slndrome parecido a la ciated with menlngoencephalitls during bactenal kidney 'enfermedad del torneo en truchas arco Ins Salrno galrd- disease of salmonids. Res Vet Sci 54:25-31 neru de Venezuela Slmposio FAO/CARPAS Sobre Acul- Wolf K, Marklw ME, Machado Cruz J, Galhano MH, Eiras J, cultura en America Latlna Montevideo, Uruguay, 26 de Herman RL (1981) Non-n~yxosporidanblacktail of salmon- noviembre a1 2 de diciembre de 1974 CARPAS/6/74/SE ids. J Fish DIS 4.355-357

Responsjble Subject Edltor: W. Korting, Hannover, Germany Manuscript first rece~ved.July 7, 1995 Revised verslon accepted. October 24, 1995 162 Dis Aquat Org 26: 159- 162, 1996

values were not only lower than by neutralization, but LITERATURE CITED also under 20 in 2 cases (serological relatedness of SBR with GSV and CRV). This disparity between results Ahne W, Kolbl 0 (1987) Occurrence of reovirus In European cyprinid fishes (Tinca tinca Lin.; Leuciscus cephalus Lin.). from the 2 techniques could be due to involvement of J Appl Ichthyol3:139-141 different epitopes in the -antigen reactlon. Archetti I,Horsfall FL (1950) Persistent antigenlc variation of In a previous study Dopazo et al. (1992) found some the influenza A viruses after incomplete neutralization in relationship between neutralization ratios and RNA vivo with heterologous immune serum. J Exp Med 92: 44 1-462 profiles of several aquareovirus strains, and estab- Brady YJ, Plumb JA (1988) Serological comparison of golden lished that cross-neutralization is the best tool for shiner virus, virus, reovirus 13P2 and catfish studying serological relatedness among aquareo- reovirus. J Fish Dis 11:44 1-443 viruses. The results presented here agree with that Dopazo CP, Toranzo AE, Samal SK, Roberson BS, Baya A, conclusion. On the other hand, since the values are Hetrick FM (1992) Antigenic relationships among rota- '/, viruses isolated from fish. J Fish Dis 15:27-36 usually lower by immunodot than by neutralization Hedrick RP, Rosemark R, Aronstein D, Winton JR, McDowell tests, as shown in the present study and In previous T, Amend D (1984) Characteristics of a new reovirus from reports (Dopazo et al. 1992), perhaps the criterion for channel catflsh (Ictalurus punctatus). J Gen Virol 65: .IJLI -,.- -1334 . --. determining serogroups by neutralization (l/, > 20) Ishiguru S, Izawa H, Kodama H, Onuma M, Mikami T (1984) should be changed for immunodot data. Finally, it Serological relationships among five strains of infectious appears that the serogroups determined by cross-neu- pancreatic necrosis virus. J Fish Dis 7:127-135 tralization correlate with the genogroups established ~nrgensenPEV (1972) Freund's adjuvants: thelr influence on by Lupiani et al. (1993); however, further studies the speclflcity of viral antisera. Acta Path01 Mcrobiol including a larger number of aquareovirus strains must Scand Sec B 80:931-933 Lupiani B, Hetrick FM, Samal SK (1993) Genetic analysis of be conducted to confirm that conclusion. aquareoviruses using RNA-RNA blot hybridization. Virol- ogy 197:475-479 Okamoto N, Sano T, Hedrick RP, Fryer JL (1983) Antigenlc Acknowledgements. This work was supported by Grants relationships of selected strains of infectious pancreatic XUGA 20002A94 from Xunta de Galicia and MAR 89-0270 necrosis virus and European eel virus. J Fish Dis 6119-25 from the Comision Interministerial de Ciencia y Tecnologia Reed U, Miiench H (1938) A simple method of estimating (CICYT), Spain. fifty percent endpoints. Am J Hyg 27:493-497

Responsible Sublect Editor: E WM.Hetrick, College Park, Manuscript first received: January 16, 1996 Maryland, USA Revised version accepted: May 21, 1996

Erratum

Re: L. Margolis, M. L. Kent, P. Bustos "Diseases of salmonids resembling myxosporean whirling disease, and the absence of Myxobolus cerebralis, in South America" Dis Aquat Org 25: 33-37 (1996)

An error occurred in the first author's initials. The correct form is given above